Abstract
Keywords
Chaos, Seat, Comfort / Muscular Fatigue, Electromyogram, Long-term Sitting
Abstract
One of important problems in automotive seats is how to evaluate, and further-more to reduce the driver fatigue caused due to long hours of driving. This study proposes a method to approach these questions that we have often faced. That is, is there any objective method that can be used to evaluate the driver fatigue during sitting on a seat ? The recent findings that myoelectric signals, as well as other biological rhythms (electrocardio- graphic wave, EEG, etc.), have non-linear dynamics and chaotic features, implicates a possible promising objective evaluation method for driver fatigue, in terms of chaotic analysis of biological signals. The purpose of this paper is that, through the complexity analysis based on chaotic dynamics of the electromyogram (EMG), it is to characterize the changes in driver fatigue during long hours of driving.
By measuring the drivers EMG, we tried to evaluate his muscular fatigue during 90 minutes of simulated driving task. The signals were measured at the erector muscle of spine by using 2 seats; one is non-fatiguing seat (seat A), the other is fatiguing seat (seat B). In this objective evaluation, chaotic features of the EMG data were analyzed by the method of reconstructed phase portrait, and by the estimations of the Largest Lyapunov Exponent ë 1, and Correlation Dimension. In the final of analysis, subjective evaluations of both physically and mentally fatigue were conducted for each seat. As for the Reconstructed Phase Portrait, the attractors of both seats are shown for every 30 minutes measurement. When observing their attractors, a periodicity trend can be seen as the time passes in B (fatiguing) seat, which means a decrease in the chaotic nature. In conclusion, it showed that the chaotic nature in seat A having higher values of ë 1 increased than in seat B.
One more thing we have to do is to confirm the agreement between the objective evaluation result and the subjective evaluation result. In comparison the sustaining ratio obtained by the sensory (subjective) evaluation, which represents the scores of the physical fatigue during the simulated driving task, with the results of the objective evaluation (Correlation Dimension and the largest Lyapunov Exponent), the similar changes during the driving task are recognized, including the differences between non-fatiguing seat and fatiguing seat. This study proves that there is an effective way to show the objective evidence for non-fatiguing seat!